Put the verbs in the past form, then change them in to negative and question.
1) They (be) happy yesterday.
+)______________
-)__________________
?)________________
2) We (go) swimming last summer.
+)...........................
-)............................
?).....................
3) The students (be) in the school yard 2 hours ago.
+)................................
-).......................
?).........................
4) Lan (buy) a new lantern last night.
+)............................................
-)................................................
?)............................................
GIÚP MÌNH VỚI !!!